CREODONTA. 285 



separated from each other on all the true molars. The internal cusp is 

 the apex of a V, each limb of which is continued into a cingulum along the 

 anterior and posterior base of the crown. The external base of the first 

 true molar is subequally bilobate, on the second the anterior lobe is pi-o- 

 duced, and on the third the posterior lobe is only represented by a right 

 angle between the external and posterior borders of the crown, which are 

 of equal length. The second principal cusp is also reduced. Canines well 

 developed. Enamel smootli. 



Measurements. 



M. 



Length of superior molar series 0216 



Length of superior true molars 0107 



Diameters of second true molars ^'*°*"°P''«*«'i''^ «033 



c transverse 0055 



Width of jaws at same tooth 022 



Width bet ween bases of canines 008 



Depth of ramus mandibuli at Pm. i 005 



Depth of ramus mandibuli at M._iii 009 



From the Wasatch Eocene of the Big-Horn River; J. L. Wortman. 



This species was an opossum-like animal of the size of the American 

 weasel, Mustela americana. Its delicately acute teeth indicate a diet of in- 

 sects, which no doubt abounded during the Wasatch epoch. 



STYPOLOPHUS Cope. 



Stypolophus Cope, Second Account New Vertebrata Bridger Eocene (Paleoutological Bulletin, No. 2), p. 

 1, Aug. 3, 1872, Proceed. Amer. Philos. Soc, 1872, p. 446; An. Eep. U. S. Geol. Surv. Terrs., 1872, 

 p. 559. Protoiomus Cope, Rep. Vert. Foss. New Mexico, 1874, p. 13; System. Cat. Vert. Eocene 

 New Mexico, U. S. Geol. Surv. W. of lOOtb Mer., 1875, p. 9. Cyiiohi/a-nodon Filhol, Comptes 

 Eendus de la Soci^t^ Philomathlque, Paris, 1873. Eecherches sur 1. Phosphorites du Quercy, 

 1877, 227. 



Molars seven below, i. e., four premolars and three true molars, and prob- 

 ably the same number above. Inferior true molars, consisting of three eleva- 

 ted cusps in front and a low horizontally-expanded heel behind; the external 

 cusp largest, the internal smallest, and the anterior intermediate, forming with 

 the external a short sectorial blade. The inferior premolars two-rooted 

 (the first only seen in S. caylusi, S. whitice, and 8. Mans) ; the crown con- 

 sisting of a compressed cusp and short trenchant heel. Of the superior 

 molars the last is narrow, transverse, and with a blade-like crown. The 

 two preceding have crowns forming right-angled triangles in horizontal sec- 



